Center bearing assembly including support member containing rheological fluid

ABSTRACT

A center bearing assembly includes a roller bearing adapted to receive and rotatably support a coupling shaft and a bracket adapted to be secured to a vehicle frame. A support member is provided which supports the roller bearing within the bracket. The support member includes a bladder formed of an elastomeric material. The bladder contains a rheological fluid which exhibits a significant change in its ability to flow or shear upon the application of an appropriate energy field. Preferably, the bladder contains a magneto-rheological magnetic fluid. By varying the power supplied to an electromagnetic located adjacent the bladder, the vibration dampening characteristics of the support member may be varied depending upon the operating conditions of the vehicle.

BACKGROUND OF THE INVENTION

The invention relates in general to bearings for supporting shafts forrotation and in particular to an improved structure for a center bearingassembly for rotatably supporting an intermediate portion of a vehicledrive line or coupling shaft assembly.

In most rear wheel drive vehicles, a source of rotational energy, suchas an internal combustion or diesel engine, is located near the front ofthe vehicle. The engine is connected by means of a drive line to rotateone or more driven wheels located near the rear of the vehicle. Thedrive line typically extends between a transmission, which is connectedto the engine, and a differential, which is connected to the drivenwheels. In some vehicles, the distance separating the transmission andthe differential is relatively short. In these vehicles, the drive lineis composed of a single tube, usually referred to as the drive shaft. Inother vehicles, the distance separating the transmission and thedifferential is relatively long, making the use of a single drive shaftimpractical. In these vehicles, the drive line is composed of a driveshaft and one or more coupling shafts. The coupling shafts are connectedto the drive shaft (and to each other) by universal joints.

Drive lines which are composed of a drive shaft and one or more couplingshafts require the use of one or more intermediate resilient supportstructures, which are generally referred to as center bearingassemblies. A typical center bearing assembly includes an annular rollerbearing within which the coupling shaft is rotatably supported. Theroller bearing itself is disposed within a generally annular resilientsupport member. The resilient support member is, in turn, disposedwithin a relatively rigid, generally U-shaped bracket which is securedto the lower surface of a cross member extending between the side railsof the vehicle frame.

The resilient support member is provided to reduce vibrations of thedrive line in the vicinity of the center bearing assembly and to preventsuch vibrations from being transmitted to the vehicle frame. In thepast, the resilient support member has been formed from an elastomericmaterial, such as rubber. Under most vehicle operating conditions, knownrubber support members are effective in substantially reducing thetransmission of vibrations for the drive line to the vehicle frame.However, the vibration dampening characteristics of such known supportmembers, which depend upon the specific material and the particularconfiguration thereof, remain constant regardless of the vehicleoperating conditions. Accordingly, the vibration dampeningcharacteristics of known support members can be optimized only for asingle set of operating conditions. The vibrations generated by thedrive line, on the other hand, constantly change with changes in theoperating conditions of the vehicle. As a result, these support membersmay not provide optimum vibration dampening of vibrations under varyingoperating conditions. It would, therefore, be desirable to provide animproved structure for a center bearing assembly which includes asupport member having vibration dampening characteristics which can beadjusted in accordance with the changing operating conditions of thevehicle.

SUMMARY OF THE INVENTION

The invention relates to a center bearing assembly adapted to rotatablysupport a rotatable shaft on a vehicle frame. The center bearingassembly includes an annular roller bearing, which is adapted to receiveand rotatably support the rotatable shaft, and a bracket which adaptedto be secured to the vehicle frame. A support member is provided whichsupports the roller bearing within the bracket. The support memberincludes a bladder which is formed of an elastomeric material and whichcontains a rheological fluid. The term "rhelogical fluid" is used hereinto describe any fluid which exhibits a significant change in its abilityto flow, or shear, upon the application of an appropriate energy field,such as electrical or magnetic fields. Thus, the novel construction ofthe invention provides an effective center bearing assembly supportmember having vibration dampening characteristics which may be variedwith the changing operating conditions of the vehicle.

Various objects and advantages of this invention will become apparent tothose skilled in the an from the following detailed description of thepreferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of a center bearing assembly inaccordance with this invention.

FIG. 2 is a cross sectional view of the center bearing assembly takenalong line 2--2 of FIG. 1.

FIG. 3 is a block diagram of a control system for the center bearingassembly illustrated in FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, there is illustrated in FIGS. 1 and 2 acenter bearing assembly, indicated generally at 10, in accordance withthis invention. As is well known in the art, the center bearing assembly10 is adapted to rotatably support a rotatable shaft 11 or similarcomponent of a multiple piece vehicle drive line on the lower surface ofa cross member 12 or other portion of a frame for a vehicle. Toaccomplish this, the cross member 12 is formed having a pair of threadedapertures 13 and 14 for securing the center bearing assembly 10 thereto,in a manner which will be described in detail below. The generalstructure and operation of the center bearing assembly 10 is well knownin the art and, for the sake of brevity, will not be discussed in detailherein. U.S. Pat. No. 4,392,694 to Reynolds, owned by the assignee ofthis invention, discloses the general structure and operation of centerbearing assemblies, and the disclosure thereof is incorporated herein byreference.

The center bearing assembly 10 includes a bracket, indicated generallyat 20. The bracket 20 includes a generally annular body portion 21 and apair of opposed, outwardly extending leg portions 22 and 23. As bestshown in FIG. 2, the body portion 21 of the bracket 20 is preferablyformed having a substantially U-shaped cross sectional shape forproviding strength thereto. The leg portions 22 and 23 may be formedintegrally with the body portion 21 as shown, or alternatively may besecured to the body portion 21 by welding or any other suitable method.Respective apertures 22a and 23a are formed through the ends of the legportions 22 and 23. The apertures 22a and 23a formed through the legportions 22 and 23 of the bracket 20 are spaced apart from one anotherby the same distance as the apertures 13 and 14 formed in the crossmember 12. Thus, as will be explained in detail below, the apertures 22aand 23a can be aligned with the apertures 13 and 14 to permit thebracket 20 to be secured to the cross member 12 of the vehicle frame.

A reinforcing bar 24 is disposed between the bracket 20 and the crossmember 12. The reinforcing bar 24 includes a central body portion 25 anda pair of end portions 26 and 27. The central body portion 25 is formedhaving a 25 recess 25a, within which a portion of the annular bodyportion 21 of the bracket 20 extends. Respective apertures 26a and 27aare formed through the end portions 26 and 27 of the reinforcing bar 25.The apertures 26a and 27a formed through the reinforcing bar 25 arespaced apart from one another by the same distance as the apertures 13and 14 formed in the cross member 12. Thus, the apertures 26a and 27acan be aligned with the apertures 22a and 23a and with the apertures 13and 14 to permit the bracket 20 to be secured to the cross member 12 ofthe vehicle frame by suitable threaded fasteners 30. The threadedfasteners 30 extend through the aligned apertures 22a, 26a, and 13 andthrough the aligned apertures 23a, 27a, and 14 to secure the bracket 20and reinforcing bar 24 to the cross member 12.

The center bearing assembly 10 further includes a support member,indicated generally at 30. As best shown in FIG. 2, the support member30 is embodied as a bladder 31 formed from a flexible elastomericmaterial. The bladder 31 is generally annular in shape, having an outercircumferential surface which is secured to an inner circumferentialsurface of the body portion 21 of the bracket 20. The bladder 31 may bemolded directly to the bracket 20, or may be secured thereto in anyother suitable manner, such as with an adhesive. The innercircumferential surface of the bladder 31 defines an enlarged axiallyextending opening 32 formed through the center thereof, the purpose ofwhich will be explained below. An annular cavity 31a is defined withinthe bladder 31. The annular cavity 31a of the bladder 31 is filled witha suitable rheological fluid 33.

As mentioned above, the term "rheological fluid" as used herein refersto a fluid which exhibits a significant change in its ability to flow orshear upon the application of an appropriate energy field. In thepreferred embodiment, the rheological fluid is a magneto-rheological(MR) fluid, which is responsive to the presence of a magnetic field forchanging is ability to flow or shear. MR fluids are formed ofmagnetizable particles, such as carbonyl iron, in a fluid carrier, suchas a silicone oil. When exposed to a magnetic field, the particles alignand reduce the ability of the fluid to flow. The shear resistance of theMR fluid is a function of the magnitude of the applied magnetic field.MR fluids are preferred for use in this invention because they arecapable of generating relatively high fluid shear stresses and can becontrolled using power supplies which are normally available invehicles. TRW MR fluid, which is commercially available from TRW, Inc.,is an example of one known rheological fluid which has been foundsuitable for use in this invention. However, other rheological fluidscan also be used in accordance with this invention. For example,electro-rheological (ER) fluids, which are responsive to the presence ofan electrical field (such as voltage) may also be used.

Means are provided for selectively generating and applying an energyfield to the rheological fluid. The specific nature of this means willdepend upon the particular type of rheological fluid is selected foruse. In the preferred embodiment, where the rheological fluid is an MRfluid, the means for selectively generating an energy field can includeone or more electromagnetic coils 35 provided proximate the bladder 32containing the MR fluid 33. The electromagnetic coils 35 may be arrangedin any manner such that when energized, a magnetic field is applied tothe MR fluid 33. The electromagentic coils 35 are preferably arranged sothat the applied magnetic field is generally uniform over the interiorof the bladder 32 containing the MR fluid 33. The electromagnetic coils35 are preferably circumferentially embedded in or otherwise supportedon the support member 30. The coils 35 are connected to a power supplythrough electrical conductors (not shown). By varying the magnitude ofthe power supplied to the electromagnetic coils 35, the strength of themagnetic field applied to the MR fluid 33 can be varied. As a result,the resistance to flow or shear of the MR fluid 33, which affects thevibration dampening characteristics of the support member 30, can bevaried. The means by which the power supplied to the electromagneticcoils 35 is controlled is described below.

An annular bearing seat 40 is secured within the central opening 31a ofthe bladder 31. The bladder 31 may be molded directly to the bearingseat 40, or may be secured thereto in any other suitable manner, such aswith an adhesive. An annular roller bearing 50 is mounted in the bearingseat 40. The roller bearing 50 is typically a ball type roller bearing,but may be any suitable antifriction bearing. One end of the rotatableshaft 11 of the vehicle drive line is received and rotatably supportedin the roller bearing 50.

As mentioned above, by varying the magnitude of the power supplied tothe electromagnetic coils 35, the vibration dampening characteristics ofthe support member 30 can be changed. Such changes are preferablyeffected in response to a change in one or more of the operatingconditions of the vehicle. To accomplish this, sensors are provided forsensing one or more operating conditions of the vehicle. Referring toFIG. 3, it can be seen that a plurality of sensors 60, 61, and 62 can beprovided for monitoring the status of the vehicle operating conditionsand for generating electrical signals which are representative thereof.For example, some of the vehicle operating conditions which can bemonitored by the sensors 60, 61, and 62 can include the vehicle speed,vehicle acceleration, rotational speed of the shaft 11, angulardisplacement of the shaft 11, radial acceleration of the center bearing50, axial acceleration of the center bearing 50, radial displacement ofthe center bearing 50, and axial displacement of the center bearing 50.If desired, however, other operating conditions of the vehicle may alsobe sensed and used to control the vibration dampening characteristics ofthe support member 30.

Each of the sensors 60, 61, and 62 is connected to an electronic circuit70. The electronic control circuit 70, which may be embodied as anyconventional microprocessor or similar computing device, is programmedto continuously read the electrical signals from the sensors 60, 61, and62 and to generate an electrical control signal in response to apre-programmed algorithm. The algorithm used by the electronic controlcircuit 70 can be easily derived using known vibration data or bytesting on the vehicle. In the simplest embodiment of the invention, asingle sensor 60 is used to monitor a single vehicle operatingcondition. By measuring the amount of vibration which is generated forgiven value of the sensed operating conditions, a look-up table can becreated which correlates the value of the sensed operating conditionwith a value for the control signal which will minimize the generationof such vibration. The same procedure can be followed when two or moreoperating conditions are sensed.

The output signal of the electronic control circuit 70 is connected to acurrent driver circuit 71. The current driver circuit 71 is conventionalin the art and is provided to convert the output signal from thecontroller 70 into a corresponding electrical current. The electricalcurrent generated by the current driver circuit 71 is fed to theelectromagentic coils 35, which generate the magnetic field in responsethereto. Thus, it can be seen that the magnitude of the output signalgenerated by the electronic control circuit 70 determines the magnitudeof the electromagnetic field generated by the electromagnetic coils 35.Consequently, the ability of the MR fluid 33 contained in the cavity 32aof the bladder 32 to flow or shear can be varied. The vibrationdampening characteristics of the support member 30 can, therefore, becontinuously varied according to the control algorithm and theinformation provided by the sensors 60, 61, and 62.

A manual control device 80 may be directly connected to the drivercircuit 71. The manual control device 80 can allow the operator of thevehicle to directly adjust the magnitude of the current supplied to theelectromagnetic coils 35. As a result, fine adjustment of the vibrationdampening characteristics of the support member 30 is permitted toreduce or eliminate any remaining vibrations transmitted to the vehicleframe. The manual control device 80 can be embodied as a simplepotentiometer or other device which, in response to manual manipulation,generates an output signal to the driver circuit 71. The manual controldevice 80 may be used in conjunction with the sensors 60, 61, and 62 andthe electronic control circuit 70, or in lieu thereof.

Additionally, it will be appreciated that the outputs of the sensors 60,61 and 62 may be connected directly to the driver electronics 71 asshown by the dotted lines in FIG. 3, thereby eliminating the need forthe electronic control circuit 70. In this arrangement, the sensors 60,61, and 62 can function in a manner similar to the manual control device80 described above, wherein the output signals therefrom are useddirectly by the driver circuit 71 to control the magnitude of theelectrical current supplied to the electromagnetic coils 35.

In accordance with the provisions of the patent statutes, the principleand mode of operation of this invention have been described in itspreferred embodiment. However, it should be noted that this inventionmay be practiced otherwise than as specifically illustrated anddescribed without departing from its spirit or scope.

What is claimed is:
 1. A center bearing assembly adapted to rotatably support a rotatable shaft on a vehicle frame comprising:a rolling bearing adapted to rotatably support the rotatable shaft; a bracket adapted to be secured to a vehicle frame; and a support member supporting said roller bearing within said bracket, said support member including a bladder containing a rheological fluid.
 2. The center bearing assembly defined in claim 1 further including means for selectively applying an energy field to said rheological fluid.
 3. The center bearing assembly defined in claim 2 wherein said rheological fluid is a magneto-rheological fluid, and wherein said means for applying an energy field includes an electromagnet.
 4. The center bearing assembly defined in claim 2 further including a sensor for sensing an operating condition of said vehicle, said means for selectively applying said energy field being connected to said sensor so as to vary said energy field in response to said operating condition.
 5. The center bearing assembly defined in claim 4 wherein said sensor senses the radial displacement of said center bearing.
 6. The center bearing assembly defined in claim 4 wherein said sensor senses the axial displacement of said center bearing.
 7. The center bearing assembly defined in claim 4 wherein said sensor senses the radial acceleration of said center bearing.
 8. The center bearing assembly defined in claim 4 wherein said sensor senses axial acceleration of said center bearing.
 9. The center bearing assembly defined in claim 4 further including a shaft rotatably mounted within said center bearing, and wherein said sensor senses the angular displacement of said shaft.
 10. The center bearing assembly defined in claim 1 further including a shaft rotatably mounted within said center bearing.
 11. The center bearing assembly defined in claim 1 wherein said bladder is generally annular in shape.
 12. A rotatable shaft and center bearing assembly adapted to rotatably mount the shaft to a vehicle frame, comprising:a rolling bearing; a shaft rotatably mounted within said roller bearing; a bracket adapted to be secured to a vehicle frame; and a support member supporting said roller bearing within said bracket, said support member including a bladder containing a rheological fluid.
 13. The rotatable shaft and center bearing assembly defined in claim 12 further including means for selectively applying an energy field to said rheological fluid.
 14. The rotatable shaft and center bearing assembly defined in claim 13 wherein said rheological fluid is a magneto-rheological fluid, and wherein said means for selectively applying said energy field includes an electromagnet.
 15. The rotatable shaft and center bearing assembly defined in claim 13 further including a sensor for sensing an operating condition of said vehicle, said means for selectively applying said energy field being connected to said sensor so as to vary said energy field in response to said operating condition.
 16. A vehicle comprising:a frame; a rolling bearing; a shaft rotatably mounted within said roller bearing; a bracket secured to said frame; and a support member supporting said roller bearing within said bracket, said support member including a bladder containing a rheological fluid.
 17. The vehicle defined in claim 16 further including means for selectively applying an energy field to said rheological fluid.
 18. The vehicle defined in claim 17 wherein said rheological fluid is a magneto-rheological fluid, and wherein said means for selectively applying said energy field includes an electromagnet.
 19. The vehicle defined in claim 17 further including a sensor for sensing an operating condition of said vehicle, said means for selectively applying said energy field being connected to said sensor so as to vary said energy field in response to said operating condition. .Iadd.
 20. A center bearing assembly adapted to rotatably support a rotatable shaft on a vehicle frame comprising:a roller bearing adapted to rotatably support the rotatable shaft; a bracket adapted to be secured to a vehicle frame; and a support member supporting said roller bearing within said bracket, said support member containing a rhelogical fluid for modifying the relative movement between said roller bearing and said bracket. .Iaddend..Iadd.21. The center bearing assembly defined in claim 20 wherein said support member includes a cavity containing said rhelogical fluid. .Iaddend..Iadd.22. The center bearing assembly defined in claim 21 wherein said support member defines an annular shaped cavity. .Iaddend..Iadd.23. The center bearing assembly defined in claim 21 further including means for selectively applying an energy field to said rheological fluid. .Iaddend..Iadd.24. The center bearing assembly defined in claim 23 wherein said rheological fluid is a magneto-rheological fluid, and wherein said means for applying an energy field includes an electromagnet. .Iaddend..Iadd.25. The center bearing assembly defined in claim 23 further including a sensor for sensing an operating condition of said vehicle, said means for selectively applying said energy field being connected to said sensor so as to vary said energy field in response to said operating condition. .Iaddend..Iadd.26. The center bearing assembly defined in claim 23 wherein said sensor senses the radial displacement of said center bearing. .Iaddend..Iadd.27. The center bearing assembly defined in claim 23 wherein said sensor senses the axial displacement of said center bearing. .Iaddend..Iadd.28. The center bearing assembly defined in claim 23 wherein said sensor senses the radial acceleration of said center bearing. .Iaddend..Iadd.29. The center bearing assembly defined in claim 23 wherein said sensor senses the axial acceleration of said center bearing. .Iaddend..Iadd.30. The center bearing assembly defined in claim 23 further including a shaft rotatably mounted within said center bearing, and wherein said sensor senses the angular displacement of said shaft. .Iaddend. 